I. Field of the Invention
Exemplary aspects of the present application generally relate to a sheet discharge device and an image forming apparatus.
II. Background Art
Conventionally, in an image forming apparatus such as a copier, a facsimile, a printer, and a printing machine, or the like, a copied material or a printed material is generated by heating and fixing an unfixed image, which is transferred and is supported on a recording medium.
On the other hand, a sheet with a fixed image often has a curl due to heating and pressure during fixing. Therefore a failure in conveyance of a sheet may occur when a curled sheet is conveyed after fixing the sheet. Conventionally, to prevent the failure in conveyance of a sheet due to a sheet jam, a sheet discharged after fixing is curled in an inverse direction of a curl. As such, the curled sheet is corrected.
JP 2009-113929 discloses a structure to correct a curl in which each of a facing roller pair has a different hardness and a rotating speed of the roller pair is changed according to a thickness and kind of a sheet.
JP 2007-217187 discloses a structure to correct a curl of a cardboard sheet or a thin sheet in which a guide plate to be curved in an inverse direction of a curl is arranged at a position just after the sheet passes a fixing device, and an angle of the plate is arranged so that a curl of the sheet is corrected.
JP 2002-12336 discloses that a conveying roller is separated from a counter roller to the conveying roller so that it is possible to remove a jammed sheet from those rollers.
However, the curl correcting mechanism which JP 2009-113929 and JP 2007-217187 disclose is arranged at a position just after where a sheet passes a fixing device. In this case, it is not considered that the sheet that has passed the curl correcting mechanism is curled again according to a shape of a conveying pass, such as an inverting pass. In other words, if a curl of the sheet corrected by the curl correcting mechanism is not completely removed at the fixing time, the sheet might be curled again in a process where the sheet moves in a curved pass.
On the other hand, in the case of JP 2002-12336, a special structure in which a roller pair is operated to contact and separate from each other is required, and this structure is not expected to remove a jam with a simple operation.